Measures of mortality

1. Measures of Mortality
Dr Inn Kynn Khaing
Lecturer, Department of Biostatistics
M.B.,B.S, MPH, MSc (Healthcare Administration) (Japan)

2. Topics to be discussed
1. Crude Death Rate
2. Age Specific Death Rate
3. Maternal Mortality Ratio
4. Mortality in early life
5. Proportional Mortality by cause
6. Proportional Mortality by age
7. Specific cause of death rate
8. Vital index

3. 1. Crude Death Rate (CDR)
 Defined as the total number of deaths in a calendar year per
1,000 mid-year estimated population (approximation to the
average population “exposed to risk” of death during the year)
CDR =
D
P
x K
D= total number of deaths registered during the calendar year
P = total mid-year estimated population or the total population of the
middle of the year i.e. as on 1st July
K = a constant usually taken as 1,000

4. 1. Crude Death Rate (CDR)
Advantages
 Shows levels of mortality in entire population (usual index of
mortality found in year books and general statistical
publications)
 Its meanings can be communicated to the general public
 Easily and quickly computed
 Even where a detailed analysis is contemplated, CDR often gives
a preliminary indication of the level or trend of mortality.

5. 1. Crude Death Rate (CDR)
Limitations
 Mixes together many population groups whose mortality varies
widely whereas the major results of mortality study have come from
examinations of these components separately by means of more
detailed analysis.
 Mixes those elements indiscriminately, in the form of an average.
 Weakness for international comparisons is that it makes no
allowance for differential age and sex compositions

6. 2. Age Specific Death or Mortality rate
(ASDR) or (ASMR)
 Defined as the number of deaths of population of the
particular age or age group during a year (Dx) per 1,000 of the
mid-year estimated population at that age or age group (Px).
 Advantageous to prepare these rates separately for males
and females “age and sex specific death rates”
 The only mean of calculation of age specific death rate that is
unaffected by the age composition of a population
ASDR =
Dx
Px
x 1,000

7. 3. Maternal Mortality Ratio (MMR)
Maternal Deaths
 defined as “the death of a woman while pregnant or within 42
days of termination of pregnancy, irrespective of the duration
and site of pregnancy, from any cause related to or aggravated
by the pregnancy or its management but not from accidental
or incidental causes”.
 Risk of dying from causes associated with childbirths is
measured by MMR

8. 3. Maternal Mortality Ratio (MMR)
Maternal mortality ratio
 defined as the No: of deaths from puerperal causes per 1000
live births.
 MMR computed by this convention is only a rough measure of
the puerperal risk, death related to live births instead of
pregnancies
MMR =
No: of deaths from puerperal causes in a given
population in a given year
No: of LBs registered in the same population in the
same area in the same year
x 1,000

9. 4. Mortality in Early Life

10. Infant Mortality Rate (IMR)
 Mortality rates among infants is of special significance: one of
the most sensitive indexes of health conditions of the general
population.
 IMR is calculated as a ratio of the number of deaths of infants
under 1 year of age to the number of live births occuring in an
area during a given year.
 This is usually multiplied by 1,000 and the IMR is expressed as
a rate per 1000 live births.

11. Infant Mortality Rate (IMR)
IMR =
for (178)
towns
No: of infant deaths of infants for (178) towns in 1974
No: of live births registered for (178) towns in 1974
IMR =
No: of deaths of infants under 1 year of age
among a population of a given area during a year
No: of live births registered among the same
population of the same area during the same year
x 1,000
Method (1) Conventional Method
x 1,000

12. Infant Mortality Rate (IMR)
Year Live Births Infant Deaths
Year 1 B1 D1
’ D1
”
Year 2 B2 D2
’ D2
”
Year 3 B3 D3
’ D3
”
IMR =
(D2
”+ D2
’)
B2
x K
Notes: the births and infant death do not all represent the same cohort

13. Infant Mortality Rate (IMR)
Method (2) Numerator Adjustment Method
Year Live Births Infant Deaths
Year 1 B1 D1
’ D1
”
Year 2 B2 D2
’ D2
”
Year 3 B3 D3
’ D3
”
 Very often not known exactly which portion of a year’s deaths belongs to
each of the 2 birth cohorts.
 2 portions may be separated approximately according to the data of
another population or to some other data of same population
IMR =
D2
” D2
’
B1 B2
x K

14. Infant Mortality Rate (IMR)
Method (2) Numerator Adjustment Method
Year Live Births Infant Deaths Infant Deaths
Year 1 B1 D1
’ D1
” D1
Year 2 B2 D2
’ D2
” D2
Year 3 B3 D3
’ D3
” D3
 f may be assigned an arbitrary value of 0.30 without danger of very
serious distortion of the mortality rate
IMR =
fD2 (1-f)D2
B1 B2
x K

15. Infant Mortality Rate (IMR)
Method (3) Denominator Adjustment Method
IMR =
D2
fB1 + (1-f)B2
x K
Year Live Births Infant Deaths Infant Deaths
Year 1 B1 D1
’ D1
” D1
Year 2 B2 D2
’ D2
” D2
Year 3 B3 D3
’ D3
” D3

16. Infant Mortality Rate (IMR)
Method (4) Average Method
IMR =
D1 + D2 + D3
B1 + B2 + B3
x K
Year Live Births Infant Deaths Infant Deaths
Year 1 B1 D1
’ D1
” D1
Year 2 B2 D2
’ D2
” D2
Year 3 B3 D3
’ D3
” D3

17. Perinatal Mortality Ratio and Perinatal
Mortality Rate
 Defined as the sum of the stillbirths (late foetal deaths) and
the infant deaths under 1 week of age i.e. the first 7 days of
life.
PMR =
No: of SBs + deaths under 1 week of age among a
population in a year
Number of LBs in the same population in the
same year
X 1,000
Perinatal Mortality Ratio

18. Perinatal Mortality Ratio and Perinatal
Mortality Rate
PMR =
No: of SBs + deaths under 1 week of age among a
population in a year
Number of LBs and SBs in the same population in
the same year
X 1,000
Perinatal Mortality Rate

19. Early Neonatal Mortality ratio
 Defined as the number of deaths of infants under 1 week
during a year per 1,000 live births during the same year
Early
neonatal =
mortality
ratio
No: of infant deaths of under 1 week of age among a
population in a year
Number of LBs in the same population in the same
year
X 1,000

20. Late Neonatal Mortality ratio
 Defined as the number of deaths of infants at 7 to 28 days of
age during a year per 1,000 live births during the same year
Late
neonatal =
mortality
ratio
No: of infant deaths at 7 through 28 days of age
among a population in a year
Number of LBs in the same population in the same
year
X 1,000

21. Post-Neonatal Mortality ratio
 Defined as the number of infant deaths at 4 to 51 weeks of
age or 1 through 11 months of age during a year per 1,000 live
births during the same year
Post
neonatal =
mortality
ratio
No: of infant deaths at 4 through 51 weeks of age
among a population in a year
Number of LBs in the same population in the same
year
X 1,000

22. Late fetal death rate or Still birth rate
 Late fetal death rate is the number of fetal deaths with stated
or presumed gestation of 28 weeks or more divided by the
sum of live births plus late fetal deaths, per 1,000 live births
plus late fetal deaths. It is also known as Still Birth Rate.
Still
birth =
ratio
No: of infant deaths of at 7 through 28 days of age
among a population in a year
Number of LBs + SBs registered in same population in
the same year
X 1,000

23. Late fetal death ratio or Still birth ratio
Still
birth =
ratio
No: of infant deaths of at 7 through 28 days of age
among a population in a year
Number of LBs registered in same population in the
same year
X 1,000

24. Comparison of Still birth ratio and Still birth rate
Still birth ratio Still birth rate
Only LBs in the denominator Both SB & LBs are included
Expressed as 1,000 LBs Expressed as 1,000 total births
Higher than still birth rate Lower than still birth ratio
Used officially by vital statistics
division, CSO, Myanmar
Not used
Internationally, comparable Not comparable

25. 4. Proportional Mortality by Cause
Proportional
cause =
mortality
Deaths due to any cause i in a year
Total deaths from all causes in a year
X 1,000
 Its use is generally limited to indicate the relative importance
of a particular cause (i) of death

26. 5. Proportional Mortality by Age
Proportional
mortality for =
any age group
of all ages
death
Deaths at any age group i in a year
Deaths of all ages in the same year
X 1,000
 Its use is generally limited to indicate the relative importance
of a particular cause (i) of death

27. 6. Specific cause of death rate
Specific cause
of death rate =
Deaths due to some particular cause
Total mid-year estimated population
X 100,000
 These ratios also referred to “cause age specific death rate”

28. 7. Case fatality rate
CFR =
No of deaths assigned to a specific disease
Number of cases of the disease
X 1000
 It predicts the risk of dying if the disease is contracted.

29. 8. Vital Index
Vital =
Index
Total no: of birth of a population in a year
Total number of deaths of a population
in the same year
X 100
 A term coined by Raymond Pearl, is the ratio of the total
number of births to the total deaths
 Indicate the extent to which the forces of natality exceeds
that of mortality at a given time (a year)

30. Calculate IMR by four different methods
Years Births Deaths
1 191998 11322
2 197003 9835
3 198016 9769